The present invention relates to a new and improved disposable absorbent products such as a urinary pad having high liquid impact capacity, high liquid retention, and which allows the skin of the wearer to remain dry.
Disposable absorbent products have been known for some time, including such products as disposable diapers, sanitary napkins, wound dressings, bandages, incontinent pads, and the like. These products incorporate an absorbent batt which is used to absorb and hold or contain body fluids. Initially in many of these products, especially diapers and sanitary napkins, the absorbent batt comprised what is termed "wadding" or plies of tissue. The wadding was disposed between a liquid-impermeable backing and a liquid-permeable facing and the plies of tissue were used to absorb and, hopefully, contain the liquid within the product. A diaper which utilizes such an absorbent batt is disclosed in U.S. Pat. No. Re. 26,151.
The wadding type of product was replaced, for the most part, by an improved absorbent batt which comprises what is termed "fluffed wood pulp fibers". This absorbent batt comprises a layer of individualized wood pulp fibers with the layer having substantial thickness. A diaper which incorporates such fluffed wood pulp absorbent batt is described in U.S. Pat. No. 2,788,003. This diaper had improved absorbent capacity and somewhat better containment than a diaper using a wadding layer. Also, the fluffed wood pulp layer is quite soft, flexible, and conformable, and, hence, produces an improved diaper over diapers using wadding as the absorbent layer.
Although fluffed wood pulp absorbent batts have a good absorptive capacity, the efficiency with which the capacity is used in a diaper or sanitary napkin is poor. The reason for this is that the fluid to be absorbed is generally deposited in a localized area within the absorbent batt, and the ability of the fluid to move along the plane of the batt is poor. The fluid tends to follow a radial wicking path and consequently moves to the closest edge of the batt where it generally is no longer contained and the product leaks.
In designing a disposable urinary device, one must be mindful of the special problems of an incontinent adult. First, the void of an adult generally is much higher in volume than that of an infant, so a device with greater absorptive capacity than that of an infant's diaper is needed. Second, a bulge under clothing is accepted by society for an infant, but the ambulatory adult with an incontinence problem longs for a product which is not visible through ordinary clothing. Third, the proportions and shape of the legs and torso of the adult differ considerably from those of an infant. Therefore, a mere enlargement of an infant diaper is not a satisfactory product.
A number of years ago, "superabsorbent materials", i.e., materials which will absorb many times their weight of liquid, were developed. Since the development of such materials, attempts to incorporate them in absorbent products such as diapers to enhance the absorption performance of these products have been made. Theoretically, a minimum amount of superabsorbent incorporated in a product would make that product perform as well or better than the prior art products. Perhaps one of the first products to incorporate such a superabsorbent material in a disposable diaper is disclosed in U.S. Pat. No. 3,670,731. This patent discloses an absorbent dressing comprising an absorbent layer sandwiched between a permeable facing and an impermeable backing sheet. The absorbent layer contains water-insoluble cross-linked hydrocolloid polymer as the superabsorbent material.
For numerous reasons, absorbent products employing superabsorbent materials as mentioned above have not to date met with great commercial success. Although the presence of the superabsorbent materials should greatly increase the absorbency of the product, difficulties in processing the materials and in designing a product in which the superabsorbent is evenly dispersed have proven difficult. There thus remains a need for highly absorbent materials which do not pose these problems.
The use of peat moss, in combination with other fibrous materials, for use in absorbent products has previously been suggested. U.S. Pat. No. 4,170,515 to J-M Lalancette discloses a method for bleaching peat moss, thereby making it suitable for use in absorbent dressings and the like. U.S. Pat. No. 4,226,237 to Y. Levesque discloses a layered absorbent structure including a first layer comprising cellulose fibers and, adjacent to the first layer, a second layer comprising, in admixture, peat moss and finely ground mechanical wood pulp. U.S. Pat. Nos. 4,215,692 and 4,507,122, both issued to Levesque, disclose that peat moss, in combination with mechanical wood pulp, can be formed into a low density board, dried, and then compressed to form a thin, flexible, absorbent board which may be used directly in absorbent products. U.S. Pat. No. 4,473,440 to Ovans discloses a peat moss containing board which is manufactured by first conditioning the board to a specific water content and then densifying the board by calendaring between rollers. U.S. Pat. No. 4,676,871 discloses an air laid peat moss board suitable for use in absorbent products which is made by harvesting and individualizing peat moss, drying the peat moss, entraining the peat moss in a gas stream, and then condensing the entrained peat moss to form a low density board. The disclosures of each of these patents are herein incorporated by reference.
Numerous designs for disposable urinary devices have been suggested, none of which, however, utilize a peat moss absorbent element. U.S. Pat. No. 4,685,914 discloses a disposable urinary pad which utilizes superabsorbent material. The pad disclosed in this patent comprises a liquid-impermeable, substantially flexible shell containing a superstructure consisting essentially of a fibrous web of hydrophobic, wet resilient, dry resilient fibers and an absorbent medium in intimate contact with at least a portion of said superstructure and at least a portion of said shell. In a preferred embodiment, the superstructure is a corrugated fibrous web, e.g., of polyester fibers, and the absorbent medium is a superabsorbent material.
U.S. Pat. No. 4,501,586 discloses an absorbent structure comprising a moisture-impermeable backing, an absorbent batt and a moisture-permeable cover covering at least the side opposite the moisture-impermeable backing. The absorbent batt is of loosely-compacted, cellulosic fibers and is provided with a reservoir having a capacity of at least 10 cc. The reservoir is formed by compression of the fibers in the reservoir zone and is located so that the product, when worn, retains the proper shape.
U.S. Pat. No. 4,731,070 discloses an absorbent article particularly suitable for use by male and female incontinents. The absorbent article includes a urine receptacle pocket offset to one end of the product and formed by folding the product and adhering together portions of a moisture impervious sheet that are folded over side marginal edges of an absorbent batt.
The present invention provides a new and improved absorbent product which possesses a large storage capacity, which is soft and comfortable, which can be designed so as not to be apparent through normal clothing and which utilizes the substantial absorptive capacity of peat moss materials.